From Angelsplus.com:
My angel fish have developed a large, bubble-like growth on their lips. They are having difficulty eating. What is this? What you're seeing is probably a lip fibroma. There is a study that suggests this is caused by a virus, that only activates when the angelfish is under stress. There is some evidence that it usually affects female angelfish, or at least that they are more susceptible. There is no cure, just as the cure for most viruses have not been found. I would not try to use such an angelfish as a breeder, because no one knows if there is a genetic factor influencing the angel fish's susceptibility to this virus. Euthanasia is generally recommended to prevent a slow death by starvation. However, some have reported being able to carefully cut the growth off and not have it re-grow.
Maybe this can help?